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[lld][elf] Skip BP ordering input sections with null data #149265

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Jul 18, 2025
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[lld][elf] Skip BP ordering input sections with null data #149265

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[lld][elf] Skip BP ordering input sections with null data
Colibrow Jul 17, 2025
f0944cc
Address comments.
Colibrow Jul 17, 2025
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6 changes: 3 additions & 3 deletions lld/ELF/BPSectionOrderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -76,10 +76,10 @@ DenseMap<const InputSectionBase *, int> elf::runBalancedPartitioning(
if (!d)
return;
auto *sec = dyn_cast_or_null<InputSection>(d->section);
// Skip empty, discarded, ICF folded sections. Skipping ICF folded sections
// reduces duplicate detection work in BPSectionOrderer.
// Skip empty, discarded, ICF folded sections, .bss. Skipping ICF folded
// sections reduces duplicate detection work in BPSectionOrderer.
if (!sec || sec->size == 0 || !sec->isLive() || sec->repl != sec ||
!orderer.secToSym.try_emplace(sec, d).second)
!sec->content().data() || !orderer.secToSym.try_emplace(sec, d).second)
return;
rootSymbolToSectionIdxs[CachedHashStringRef(
lld::utils::getRootSymbol(sym.getName()))]
Expand Down
21 changes: 15 additions & 6 deletions lld/test/ELF/bp-section-orderer.s
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Expand Up @@ -26,28 +26,28 @@

# RUN: ld.lld -o out.s a.o --irpgo-profile=a.profdata --bp-startup-sort=function
# RUN: llvm-nm -jn out.s | tr '\n' , | FileCheck %s --check-prefix=STARTUP
# STARTUP: s5,s4,s3,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d3,d2,d1,{{$}}
# STARTUP: s5,s4,s3,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d3,d2,d1,g1,{{$}}

# RUN: ld.lld -o out.os a.o --irpgo-profile=a.profdata --bp-startup-sort=function --symbol-ordering-file a.txt
# RUN: llvm-nm -jn out.os | tr '\n' , | FileCheck %s --check-prefix=ORDER-STARTUP
# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,merged1,merged2,_start,d3,d2,d4,d1,{{$}}
# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,merged1,merged2,_start,d3,d2,d4,d1,g1,{{$}}

# RUN: ld.lld -o out.cf a.o --verbose-bp-section-orderer --bp-compression-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-FUNC
# RUN: ld.lld -o out.cf.icf a.o --verbose-bp-section-orderer --bp-compression-sort=function --icf=all --gc-sections 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-ICF-FUNC
# RUN: llvm-nm -jn out.cf | tr '\n' , | FileCheck %s --check-prefix=CFUNC
# CFUNC: s5,s4,s3,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d3,d2,d1,{{$}}
# CFUNC: s5,s4,s3,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d3,d2,d1,g1,{{$}}

# RUN: ld.lld -o out.cd a.o --verbose-bp-section-orderer --bp-compression-sort=data 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-DATA
# RUN: llvm-nm -jn out.cd | tr '\n' , | FileCheck %s --check-prefix=CDATA
# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,_start,d4,d1,d3,d2,{{$}}
# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}

# RUN: ld.lld -o out.cb a.o --verbose-bp-section-orderer --bp-compression-sort=both 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
# RUN: llvm-nm -jn out.cb | tr '\n' , | FileCheck %s --check-prefix=CBOTH
# CBOTH: s5,s3,s4,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d1,d3,d2,{{$}}
# CBOTH: s5,s3,s4,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d1,d3,d2,g1,{{$}}

# RUN: ld.lld -o out.cbs a.o --verbose-bp-section-orderer --bp-compression-sort=both --irpgo-profile=a.profdata --bp-startup-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
# RUN: llvm-nm -jn out.cbs | tr '\n' , | FileCheck %s --check-prefix=CBOTH-STARTUP
# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d1,d3,d2,{{$}}
# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}

# BP-COMPRESSION-FUNC: Ordered 9 sections ([[#]] bytes) using balanced partitioning
# BP-COMPRESSION-ICF-FUNC: Ordered 8 sections ([[#]] bytes) using balanced partitioning
Expand Down Expand Up @@ -108,6 +108,7 @@ d3
d2

#--- a.c
int g1;
const char s5[] = "engineering";
const char s4[] = "computer program";
const char s3[] = "hardware engineer";
Expand Down Expand Up @@ -377,6 +378,14 @@ d1:
.word 6 // 0x6
.size d1, 16

.type g1,@object // @g1
.section .bss.g1,"aw",@nobits
.globl g1
.p2align 2, 0x0
g1:
.word 0 // 0x0
.size g1, 4

.section ".note.GNU-stack","",@progbits
.addrsig
.addrsig_sym F
Expand Down